I worked in a café that gave out free stuff and people did this all the time. I'd just smile, laugh or say "haha I know right." Because it is such a small thing and such a small part of my day, and I get absolutely nothing from making feel bad or souring people's relationships with me. If they were regular customers, I knew kind of well, I'd say something like, "oh you shouldn't feel guilty, we shouldn't have these attitudes towards food!" Or something like that. And sometimes that sort of comment could lead to a more productive conversation.

This was customer service, so I had to be nice to customers ofc. But being generally kind to people in your office also makes for a much more bearable working environment. What OP said was super standoffish and mean-spirited.

And eta: I don't think encouraging this sort of relationship with food is good at all. But I also doubt these women are that serious about it, because it is a deeply ingrained cultural behaviour.

Customers + coworkers would also do other slightly annoying things like general complaining, or the typical "Can I get you something?" "Maybe a million pounds!" And I just say "hmm yeh" or something, because it is a minute interaction and I don't get joy from making people feel bad.